STFU && RTFM

Over the last year or so I’ve had at least fifteen users complain that when they double-click an Excel document in Windows Explorer, Excel opens, but no workbook. They then have to open the document manually in Excel.
 
Here’s how to resolve this problem:
 

1. Open excel, then open a blank workbook
2. Go to Tools -> Options -> General
3. Remove the check mark from the box marked “Ignore other applications”